Standard test methods for determining one-dimensional consolidation properties of soils using incremental loading in accordance with ASTM D2435, or AASHTO . . . , and of those of other international and organizations, do not accurately predict the consolidation properties such as values of vertical settlement, coefficients of consolidation in horizontal (ch) and vertical directions (cv), and modulus of elasticity (E); because fixed ring used in these tests do not allow horizontal displacement and dissipation of excess pore-water pressures in horizontal direction, whereas, in field, under application of a vertical load, both horizontal and vertical settlements occur along with dissipation of excess pore-water pressures in both vertical and horizontal directions. To overcome this more than 100 year old problem, the inventor (Dr. Ramesh Chandra Gupta, Ph. D., P.E.) has invented a test device for determining three-dimensional consolidation properties of soils, using a flexible ring which permits development of horizontal and vertical displacements, and dissipation of excess pore-water pressures in both horizontal and vertical directions, along with increased lateral resistance as takes place in field at any depth in a soil deposit when a vertical load is applied at the surface,
The flexible ring consists of filter fabric around the soil specimen, rubber membrane around the filter fabric, circular segmental metal plates around the membrane and elastomeric rubber bands or spring loaded jacket around the segmental plates to allow horizontal and vertical displacements, dissipation of excess pore-water pressures in horizontal and vertical directions, and increased lateral resistance with each increment of vertical load. Therefore, new test device, which simulates field condition, shall allow accurate determination of three-dimensional consolidation properties of soils (such as vertical and horizontal settlements, coefficients of consolidation (cv and ch) in horizontal and vertical directions and modulus of elasticity.
For this new test device, conventional incremental consolidation frame shall be used for applying vertical load increments, each to be maintained for 24 hours for allowing dissipation of excess pore-water pressures. Triaxial type chamber system shall also be used after suitably modifying to adapt new 3-D consolidation device. With triaxial type chamber system, some modifications shall also be done to adapt to Incremental consolidation frame in place of triaxial loading system to compare which is more suitable of these two loading systems for three-dimensional consolidation tests.